This invention relates to a plastic collar integral with the outer jacket of a cable. More particularly it relates to a plastic collar melt bonded to a cable jacket for providing a seal for cable splice closure as well as strain relief for the cable.
In field installation of telephone cable, it is often necessary to splice the ends of cables together. The actual splice connections are made between the ends of the corresponding communication conductors within each cable. A portion of the jacket and shield are removed from the ends of each cable to be spliced, exposing the conductors to moisture. In order to avoid corrosion of the conductors and other hazards, it is necessary to enclose the spliced conductors with a cable splice closure. A splice closure normally includes a hollow shell having two halves. An example of a standard telephone splice closure 1 is shown in FIG. 1.
It is highly desirable to properly seal the splice closure to ensure that moisture will not leak into the closure causing the abovementioned corrosion of the conductors as well as deterioration of the conductor insulation and possibly the shield. Furthermore, it is desirable to provide strain relief for the cable so that the connected conductors do not pull apart under mechanical load.
In one mode of the present state of the art, telephone cables have been prepared for splicing by wrapping a sticky tape, such as B-sealing tape, about the cable jacket near the end to be spliced. The tape-wound end of the cable 2 was placed in contact with the inside of ends 3 of the splice closure indicated in FIG. 1. The tape was put under compression when the halves of the splice closure were secured together by screws 4 in an effort to moisture-seal the ends of the closure. Strain relief ring clamps were also clamped tightly about the cable and connected to the splice closure ends in an attempt to prevent the wire splice connections from coming loose when the cable was under load.
It has been found, however, that the use of these seal and strain relief techniques often does not work well. The adhesive bond between the tape and jacket is of insufficient strength, thus with the cable under tension, the tape quite often works itself loose thus allowing moisture to penetrate the closure. Furthermore, to properly fill the inside of the end 3 of splice closure with tape requires care, i.e., wrapping the cable with the particular number of turns and in a precise manner for a particular cable diameter and closure size. Quite often the tape is not properly wrapped about the cable. Also, resealing the closure in the event that the closure is reentered is a cumbersome and difficult task with the use of sticky tape. It has also been found that the use of a strain relief clamp about the cable jacket has damaged the cable jacket as well as the components in the core of the cable.
In an attempt to alleviate some of these problems, splice closure sleeves have been designed which are melted onto the cable jacket by a separate heat source. Normally the heat source was an enamel copper resistance wire embedded between polyethylene folds. An example of this type splice seal approach may be seen in the Proceedings of the 24th Wire and Cable Symposium of the 18th, 19th and 20th of November, 1975, in an article entitled "Welded Polyethylene Splice Closures--A Reliable Alternative" by Dale F. Giles of the Siemans Corporation, pages 99 to 103. One of the problems with this type of splice seal is that it requires a separate heat source, such as the polyethylene heating tape with resistance wire embedded therein which must be very carefully placed with respect to the pre-molded polyethylene sleeves. Furthermore, because the heating tape is placed between the cable jacket and the sleeve, an inadequate bond between the sleeve and cable may result. Furthermore, this resistance wire technique is rather expensive and tedious to install. Also, the use of a separate heating source such as resistance wires or, in some cases, a blow torch, often damaged the cable jacket. It is, therefore, desirable to provide a cable splice seal and strain relief which overcomes the problems of the prior art.